This relates generally to electronic devices and, more particularly, to electronic devices with displays and associated backlight structures.
Electronic devices such as computers and cellular telephones have displays. Some displays such as plasma displays and light-emitting diode displays have arrays of display pixels that generate light. In displays of this type, backlighting is not necessary, because the display pixels themselves produce light. Other displays, such as liquid crystal displays, contain passive display pixels. The pixels in a liquid crystal display can alter the amount of light that is transmitted through the display to display information for a user, but do not produce light. As a result, it is often desirable to provide backlight for a liquid crystal display.
In a typical backlight structure for a display such as a liquid crystal display, a light guide plate is used to distribute backlight generated by a light source such as a light-emitting diode light source. Optical films such as a diffuser layer and brightness enhancing film may be placed on top of the light guide plate. A reflector may be formed under the light guide plate to improve backlight efficiency.
To provide satisfactory backlighting, it may be desirable to locate strips of light-emitting diodes on the top and bottom edges of a light guide plate. The top and bottom strips of light-emitting diodes are typically fixed to a metal chassis. To accommodate thermal expansion of the light guide plate, which is attached along one of its edges to the metal chassis, conventional designs incorporate relatively large air gaps (e.g., a gap of about 0.6 mm) between the light-emitting diodes and the light guide plate. The use of such large gaps can have an adverse impact on backlight efficiency. Poor backlight efficiency, in turn, may decrease power consumption efficiency and can reduce battery life in an electronic device.
It would therefore be desirable to be able to provide electronic devices with improved displays and backlights.